I have noticed an occasional confusion over the phrase ‘fair test’ and I am even ashamed to say that I have allowed it to appear in one of my booklets in an incorrect context. It is an important phrase so I would like to offer a brief explanation.
In an experiment, it is important only to change one factor at a time whilst keeping all the other conditions exactly the same. This is what it means to make an experiment fair. It is important that only the factor that you are studying (the independent variable) is able to change the outcome (the dependent variable).
There is a quite basic BBC video explaining the process here. (Which only works in the UK)
One of the ideas that gets confused with the fair test is the business of doing a particular experiment several times. The repetitions are not about fairness, they are about ensuring that the results produced are consistent. It is a way of spotting any anomalies in the data.
For a slightly more challenging look at the scientific method in general, here is a 9 minute video from the brilliant Potholer54 on YouTube.
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Questions…
- When plotting a graph to show the data collected during an experiment, how do you normally decide which variable goes on which axis?
- Variables can be continuous or discrete – what do these terms mean when applied to experimental variables?
- An experiment was performed to see how high a ball bounced on a hard floor when dropped from a height of 100 cm. The experiment was repeated five times and the data collected were 31 cm, 52 cm, 49 cm, 48 cm 50 cm & 55 cm. What is a good estimate of the height that the ball would bounce when once again dropped from a height of 1 m onto a hard floor? How did you come to your decision?
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